Effects of higher temperatures on respiration and activity of alternative oxidase (AOX) were studied in mature leaves of Ajuga reptans L. and Rhodiola rosea L. Total respiration in both A. reptans and R. rosea increased exponentially with the increasing temperature of 10 °C to 35 °C. Respiration in the presence of benzhydroxamic acid (BHAM) also increased exponentially in accordance with the increasing temperature in the leaves of both A. reptans and R. rosea. Relative activity of the alternative pathway decreased significantly in the leaves of A. reptans with increasing temperatures. However, an increase in the relative activity of the alternative pathway was detected in the leaves of R. rosea. Thermoresistance of the alternative respiratory pathway was considered to be higher in R. rosea compared to A. reptans. We suppose that A. reptans and R. rosea have different mechanisms regulating partitioning of electrons to the alternative respiratory pathway.